URINE 



497 



in urine such as ammonia, creatinine, and uric acid yield nitrogen more or less 

 rapidly when the urine is treated with hypobromite. The measurement of the gas 

 as ordinarily carried out involves considerable errors. The results are usually high, 

 and may be excessively so. Robinson and Muller 1 have suggested that the 

 ureometer be shaken for five minutes to hasten the reaction and that the results 

 as obtained be multiplied by the factor 0.917 to insure more accurate results. 

 They use the Doremus-Hinds apparatus. 



(a) Hypobromite Method (using the Doremus-Hinds Ureometer). The Doremus- 

 Hinds ureometer (Fig. 160) is one of the simplest and cheapest forms of appa- 

 ratus in general use for the determination of 



urea by the hypobromite process. It is, how- 

 ever, much less accurate than those types of 

 apparatus which involve the measurement of 

 the nitrogen in a gas burette over water with 

 equalization of pressure. In using this appa- 

 ratus proceed as follows: Fill the side tube B 

 and the lumen of the stop-cock C with the 

 urine under examination. Carefully wash out 

 tube A with water and introduce into it sodium 

 hypobromite solution, 3 being careful to fill the 

 bulb sufficiently full to prevent the entrance 

 of air into the graduated portion. Now allow 

 i c.c. of urine 2 to flow from tube B into tube A, 

 and after the evolution of gas bubbles has ceased 

 (10-20 minutes) take the reading of the gradu- 

 ated scale on tube A. 



Calculation. Observe the reading on the 

 graduated scale of tube A. This tube is so 

 graduated as to represent the weight of urea, in 

 grams, per cubic centimeter of urine. If we 

 wish to compute the percentage of urea present 

 this may be done very readily by simply moving 

 the decimal point two places to the right; e.g., if 

 the reading is 0.02 gram the urine contains 2 

 per cent of urea. 



Interpretation. See page 493. 



(b) Hypobromite Method (using Marshall's Urea Apparatus). Place the thumb 

 over the side opening of the bulbed-tube of the apparatus (Fig. 162) and carefully 

 fill the tube with sodium hypobromite solution. 3 Close the opening in the end of 

 the tube with a rubber stopper, incline the tube to allow air-bubbles to escape, and 



1 Robinson and Muller: Jour. Am. Med. Ass'n, 62, 514, 1914. 



2 If the content of urea in the urine under examination is large, the urine may be diluted 

 with water before determining the urea. If this is done it must of course be taken into con- 

 sideration in computing the content of urea. 



3 The ingredients of the sodium hypobromite solution should be prepared in the form of 

 two separate solutions. When needed for use mix one volume of solution a, one volume of 

 solution b, and 3 volumes of water. 



(a) Dissolve 125 grams of sodium bromide in water, add 125 grams of bromine and make 

 the total volume of the solution i liter. 



(b) A solution of sodium hydroxide having a specific gravity of i .250. This is approxi- 

 mately a 22.5 per cent solution. 



Preserve both solutions in rubber-stoppered bottles. 

 32 



FIG. 1 60. DOREMUS-HINDS 

 UREOMETER. 



